Did you have nausea, vomiting, diarrhea, or abdominal pain and cramps?
In that case it is possible that the symptoms that you have were due to food poisoning. And since this occurred after eating the Tesco product, it is likely that the product was the causative factor.
For this you have to visit your local general practitioner. I can only answer your question online.
This question has remained unanswered by any UK based doctor, and it is likely because doctor will typically not be willing to provide a letter stating what you want to be said. No doctor can prove that this was food poisoning. The most that can be said is that food poisoning is a possibility, but that is not proof that it was food poisoning.
It is also very possible that the symptoms that you describe could be from a community acquired viral gastroenteritis. Viral gastroenteritis infections are very common, and everyone that gets a viral gastroenteritis must have had a meal the preceded the onset of symptom, but that is not proof that the meal was the cause of the viral infection, and it typically is not.
I realize that this is not the letter that you requested, but no UK doctor has responded and I thought that you should know that no doctor can provide a letter that proves that this was food poisoning. If Tesco is willing to accept a letter saying that it is possible that this could have been food poisoning, then you should rephrase your request.
No, although you can print off the information that I provided.